492 INFECTION AND IMMUNITY. 



the various antibodies in order to obtain a correct 

 idea of its value. 



A natXm~ Although the serum of patients acquires a cer- 

 tain agglutinating power, it is rather low (1/3 or 

 1/5), and does not become manifest until during 

 the second week of the disease. Before this time 

 diagnosis by clinical or bacteriologic means can be 

 made with certainty; hence, for clinical diagnosis 

 the reaction has little value. On the other hand, 

 a strong artificial agglutinating serum obtained 

 by the specific immunization of animals is of great 

 value for the identification of the plague bacillus 

 when cultures have been obtained from suspected 

 cases. Artificial serums may agglutinate in dilu- 

 tions of from 1/1000 to 1/6000. 



B. Diseases in which acquired immunity is not 

 due to increased bactericidal power of the serum, or 

 knowledge on this point is deficient. 



I. ANTHRAX. 



From the standpoint of infection and immunity 

 anthrax is of particular interest. It is the first 

 disease of which the bacterial etiology was proved 

 and in which the specific microbe was used in pure 

 culture for the production of artificial immunity 

 (vaccination). 



Anthrax is particularly a disease of cattle and 

 sheep, and it prevails in certain European coun- 

 tries, especially Eussia, in Australia and in South 

 America. It does not occur extensively in this 

 country. Definite regions are at times heavily in- 

 fected, and it is in such localities that the disease 

 is most frequently transmitted to man. 



